The present invention relates to an air conditioning apparatus for an automotive vehicle or the like.
A typical vehicle air conditioning apparatus comprises a duct and a blower for forcing air through the duct. An evaporator of a cooler and a core of a heater are disposed in the duct and are selectively utilized. A movable temperature control door controls air flow through the evaporator and core and thereby the temperature of air flowing through the duct. The temperature control door is positioned in accordance with sensed air temperature.
It is desirable to control the speed of the blower to be low when there is little difference between the sensed temperature and the desired temperature. When this occurs, the temperature control door is in a central position. As the difference between the sensed temperature and the desired temperature increases indicating a need for air conditioning, the temperature control door is moved in one direction or the other depending on the temperature difference. It is desirable under these conditions to increase the blower speed to facilitate a faster change in temperature. It is also desirable to make the blower speed maximum when the apparatus is in the maximum cooling mode.
Typical air conditioning systems are disclosed in U.S. Pat. Nos. 3,263,739 and 3,662,818 which constitute the closest known prior art. Means are disclosed for automatically controlling the blower speed as a function of the position of the temperature control door. However, said means comprise a complicated arrangement of variable resistors, contacts and the like which is expensive to manufacture, takes up a disproportionate amount of space and is prone to frequent malfunction. In addition, these prior art disclosures do not comprise any means for automatically driving the blower at maximum speed when the apparatus is in the maximum cooling mode.